Search

Motivated by the supersymmetric interpretation of the CDF ee����plus missing energy event and the reported Z->bb excess at LEP, we analyze the Higgsino as a cold dark matter candidate. We examine the constraints as implied by the collider experiments, and then calculate its relic density. We find that this Higgsino-like lightest supersymmetric particle is a viable cold dark matter candidate (0.05 < Omega h^2 < 1), and we discuss its favorable prospects for laboratory detection., 10 pages, 3 figures, LaTeX with epsf

We have analyzed the Collider Detector at Fermilab $\mathrm{ee}\ensuremath{\gamma}\ensuremath{\gamma}+\mathrm{missing}\mathrm{energy}$ event. Its kinematics and expected rate are consistent with selectron pair production. We consider two classes of general low-energy supersymmetric theories where the lightest neutralino or the gravitino is the lightest supersymmetric particle. The supersymmetric Lagrangian is tightly constrained by the production and decay of the selectron and other data. We discuss other processes at the Fermilab Tevatron and at LEP that could confirm or exclude a supersymmetric explanation of the event.

If the reported excess (over the standard model prediction) for Z->bb from LEP persists, and is explained by supersymmetric particles in loops, then we show that (1) a superpartner (chargino and/or stop) will be detected at LEP2, and probably at LEP1.5 in 1995, (2) the basic parameter tan(beta) is at its lower perturbative limit, (3) BR(t->t1+chi0) is at or above 0.4, (4) the upper limit on m_h is considerably reduced, and (5) several important consequences arise for the form of a unified supersymmetric theory. Our analysis is done in terms of a general weak scale Lagrangian and does not depend on assumptions about SUSY breaking.

We study the most promising signals of Constrained Minimal Supersymmetry detectable at a luminosity upgraded 2 TeV Fermilab Tevatron collider. Using a full event-level Monte Carlo based on Pythia/Jetset, we simulate the trilepton signal examining in detail the effect of constraints on the parameter space. We also simulate the monolepton and dilepton signals, the missing E_T + jets signal, and the signals of stop production in supersymmetry all with full Standard Model backgrounds with realistic detector cuts. We find that large fractions of parameter space can be probed (or eliminated if no signal is found), but mass limits on charginos and neutralinos are not possible based solely on the trilepton signal. Detection efficiencies depend strongly on supersymmetry parameters beyond simply the neutralino and chargino masses; analyses (experimental or theoretical) that do not include this will draw misleading conclusions. Finally, we comment on how searches at LEP II will complement searches at Fermilab., 30 pages, LaTeX, 11 figures, now uses epsf.sty. Reference in text has been corrected; references added. Figures have been included using uufiles. Compressed PS file with embedded figures available via anonymous ftp at ftp://williams.physics.lsa.umich.edu/pub/preprints/UM-TH-95-14.ps.Z

We find that re-analyzing the LEP/SLC data with light superpartners and low $\alpha_s(\mz^2)\simeq 0.112$ yields a better fit to the data than the Standard Model, giving a satisfactory description of the $R_b$ measurement, and a better fit to $A_{LR}$. A large body of low energy ($q^2 \ll \mz^2$) data and analyses provide compelling evidence for $\alpha_s(\mz^2)\simeq 0.112$. Global fits to LEP/SLC data in the Standard Model, however, converge on a value of $\alpha_s(\mz^2)\simeq 0.126$. Recently it has become increasingly clear that these should be viewed as incompatible rather than values that can be averaged. We investigate the possibility that new physics is causing the LEP high value. To this end we have conducted a global analysis of LEP/SLC data in the Standard Model and also in the Minimal Supersymmetric Standard Model. Several predictions could confirm (or rule out) the results of this paper: light chargino and stop, top decays into stop and neutralino, large $R_b$, large $A_{LR}$, and a higher $M_W$. We briefly discuss the implications of low $\alpha_s$ for more fundamental high-scale supersymmetric theories., Comment: 12 pages, LaTeX. Available via anonymous ftp at ftp://williams.physics.lsa.umich.edu/pub/preprints/UM-TH-95-16.ps

In recent years it has been learned that scalar superpartner masses and trilinear couplings should both generically be larger than about 20 TeV at the short distance string scale if our world is described by a compactified string or M-theory with supersymmetry breaking and stabilized moduli. Here we study implications of this, somewhat generally and also in detail for a particular realization (compactification of M-theory on a G_2 manifold) where there is significant knowledge of the superpotential and gauge kinetic function, and a light gluino. In a certain sense this yields an ultraviolet completion of minimal flavour violation. Flavour violation stems from off-diagonal and non-universal diagonal elements of scalar mass matrices and trilinear couplings, and from renormalization group running. We also examine stability bounds on the scalar potential. While heavy scalars alone do not guarantee the absence of flavour problems, our studies show that models with heavy scalars and light gluinos can be free from such problems., Comment: 22 pages + references, 5 figures; v2: corrected calculation of epsilon_K (SUSY contribution is always harmless), improved presentation, added references; v3: further minor improvements, matches version to appear in EPJ C

String/M-theory is an exciting framework within which we try to understand our universe and its properties. Compactified string/M-theories address and offer solutions to almost every important question and issue in particle physics and particle cosmology. But earlier goals of finding a top–down “vacuum selection” principle and deriving the 4D theory have not yet been realized. Does that mean we should stop trying, as nearly all string theorists have? Or can we proceed in the historical way to make a few generic, robust assumptions not closely related to observables, and follow where they lead to testable predictions and explanations? Making only very generic assumptions is a significant issue. I discuss how to try to proceed with this approach, particularly in M-theory compactified on a 7D manifold of G2 holonomy. One goal is to understand our universe as a string/M-theory vacuum for its own sake, in the long tradition of trying to understand our world, and what that implies. In addition, understanding our vacuum may be a prelude to understanding its connection to the multiverse.

Assuming that the actual values of the top quark mass at FNAL and of the ratio of partial widths Z->bb/Z->hadrons at LEP are within their current one-sigma reported ranges, we present a No-Lose Theorem for superpartner searches at LEP II and an upgraded Tevatron. We impose only two theoretical assumptions: the Lagrangian is that of the Minimal Supersymmetric Standard Model with arbitrary soft-breaking terms, and all couplings remain perturbative up to scales of order 10^16 GeV; there are no assumptions about the soft SUSY breaking parameters, proton decay, cosmology, etc. In particular, if the LEP and FNAL values hold up and supersymmetry is responsible for the discrepancy with the SM prediction of the partial width of Z->bb, then we must have charginos and/or top squarks observable at the upgraded machines. Furthermore, little deviation from the SM is predicted within "super-unified" SUSY. Finally, it appears to be extremely difficult to find any unified MSSM model, regardless of the form of soft SUSY breaking, that can explain the partial width for large tan(beta); in particular, no model with top-bottom-tau Yukawa coupling unification appears to be consistent with the experiments.

Recently it has been recognized that in compactified string/M-theories that satisfy cosmological constraints, it is possible to derive some robust and generic predictions for particle physics and cosmology with very mild assumptions. When the matter and gauge content below the compactification scale is that of the MSSM, it is possible to make precise predictions. In this case, we predict that there will be a single Standard Model-like Higgs boson with a calculable mass 105 GeV $\lesssim M_h \lesssim$ 129 GeV depending on tan beta (the ratio of the Higgs vevs in the MSSM). For tan beta > 7, the prediction is : 122 GeV $\lesssim M_h \lesssim$ 129 GeV., 8 pages, 1 Figure

Arguably the best-motivated channel for early LHC discovery is events including a high multiplicity of third generation quarks, such as four top quarks. For example generic string theories compactified to four dimensions with stabilized moduli typically have light gluinos with large branching ratios to t- and b-quarks. We analyze signals and background at 7 TeV LHC energy for 1 fb{sup -1} integrated luminosity, suggesting a reach for gluinos of about 650 GeV. A non-standard model signal from counting b-jets and leptons is robust, and provides information on the gluino mass, cross section, and spin.

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables -- including some introduced here for the first time -- we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments., 10 pages, 19 figures. v2: refs updated, minor typos corrected

We point out that in theories where the gravitino mass, $M_{3/2}$, is in the range (10-50)TeV, with soft-breaking scalar masses and trilinear couplings of the same order, there exists a robust region of parameter space where the conditions for electroweak symmetry breaking (EWSB) are satisfied without large imposed cancellations. Compactified string/M-theory with stabilized moduli that satisfy cosmological constraints generically require a gravitino mass greater than about 30 TeV and provide the natural explanation for this phenomenon. We find that even though scalar masses and trilinear couplings (and the soft-breaking $B$ parameter) are of order (10-50)TeV, the Higgs vev takes its expected value and the $\mu$ parameter is naturally of order a TeV. The mechanism provides a natural solution to the cosmological moduli and gravitino problems with EWSB., Comment: 6 pages, 3 figs, V2 has additional comments

We consider a solution to the mu-problem within M theory on a G2-manifold. Our study is based upon the discrete symmetry proposed by Witten that forbids the mu-term and solves the doublet-triplet splitting problem. We point out that the symmetry must be broken by moduli stabilization, describing in detail how this can occur. The mu-term is generated via Kahler interactions after strong dynamics in the hidden sector generate a potential which stabilizes all moduli and breaks supersymmetry with m_{3/2} ~ 20 - 30 TeV. We show that mu is suppressed relative to the gravitino mass, by higher dimensional operators, mu ~ 0.1 m_{3/2} ~ 2-3 TeV. This necessarily gives a Higgsino component to the (mostly Wino) LSP, and a small but non-negligible LSP-nucleon scattering cross-section. The maximum, spin-independent cross-sections are not within reach of the current XENON100 experiment, but are within reach of upcoming runs and upgrades., Comment: 34 pages, 3 figures

We argue that CP--violation effects below a few tenths of a percent are probably undetectable at hadron and electron colliders. Thus only operators whose contributions interfere with tree--level Standard Model amplitudes are detectable. We list these operators for Standard Model external particles and some two and three body final state reactions that could show detectable effects. These could test electroweak baryogenesis scenarios., Comment: 11pp, LaTeX, UM--TH--92--27(massaged to make TeX output cleaner), no pictures

We demonstrate that in effective theories arising from a class of N=1 fluxless compactifications of M theory on a G{sub 2} manifold with low-energy supersymmetry, CP-violating phases do not appear in the soft-breaking Lagrangian except via the Yukawas appearing in the trilinear parameters. Such a mechanism may be present in other string compactifications as well; we describe properties sufficient for this to occur. CP violation is generated via the Yukawas since the soft trilinear matrices are generically not proportional to the Yukawa matrices. Within the framework considered, the estimated theoretical upper bounds for electric dipole moments of the electron, the neutron, and mercury are all within the current experimental limits and could be probed in the near future.

In recent years it has been realised that pre-BBN decays of moduli can be a significant source of dark matter production, giving a `non-thermal WIMP miracle' and substantially reduced fine-tuning in cosmological axion physics. We study moduli masses and sharpen the claim that moduli dominated the pre-BBN Universe. We conjecture that in any string theory with stabilized moduli there will be at least one modulus field whose mass is of order (or less than) the gravitino mass. Cosmology then generically requires the gravitino mass not be less than about 30 TeV and the cosmological history of the Universe is non-thermal prior to BBN. Stable LSP's produced in these decays can account for the observed dark matter if they are `wino-like.' We briefly consider implications for the LHC, rare decays, and dark matter direct detection and point out that these results could prove challenging for models attempting to realize gauge mediation in string theory., 7 pages. v3: published version

233 páginas.-- AHEP Group: et al..-- El Pdf del artículo es la versión pre-print: arXiv.1001.2693v1.-- Trabajo presentado al "The International Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC) celebrado en Boston (USA) del 2 al 4 de junio de 2009., The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a. top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades., Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the United States Department of Energy. H.D. was supported by the US Department of Energy under Grant Contract DE-AC02- 98CH10886. B.D. was supported in part by the DOE grant DE-FG02-95ER40917 and would like to thank his collaborators Richard Arnowitt, Adam Arusano, Rouzbeh Allahverdi, Alfredo Gurrola, Teruki Kamon, Nikolay Kolev, Abram Krislock, Anupam Mazumdar, Yukihiro Mimura and Dave Toback for the works related to this review. D.F. is supported in part by DOE grant DEFG92- 95ER40899. H.G. is supported in part by NSF grant PHY- 0757959 K.K. was supported by US Department of Energy contract DE-AC02-76SF00515. P.L. was supported by NSF grant PHY- 0503584 and by the IBM Einstein Fellowship. G.L. is partially supported by the U.S. Department of Energy under Grant No. DE-FG02- 91ER40688. Z.L. is supported in part by NSF grant PHY- 0653342 P.N. is supported in part by NSF grant PHY- 0757959. SUSY09 and Pre-SUSY09 were supported by NSF PHY-0834022 and de-sc0001075. B.D.N. was supported by National Science Foundation Grant PHY-0653587. E.P. was supported by the U.S. Department of Energy under contract DE-FG02-92ER-40699. J.S. is funded by MICINN and projects FPA2006-05294, FQM101, FQM437 and FQM03048. T.T. is supported in part by NSF grant PHY- 0757959. X.T. thanks the UW IceCube Group for making his visit to Wisconsin, where this report was prepared, possible. This research was supported in part by the United States Department of Energy. Work of J.F.W.V. supported by the US National Science Foundation under grant No. PHY- 0652363, by European Union ITN UNILHC (PITN-GA-2009-237920), by the Consolider Multidark project CSD2009-00064 (MICIIN), by the FPA2008-00319/FPA grant (MICIIN), by the PROMETEO/2009/091 grant (Generalitat Valenciana), by German Ministry of Education and Research (BMBF) contract 05HT6WWA, and by Colombian grant UdeA Sostenibilidad 2009-2010. C.E.M.W.’s work at ANL is supported in part by the U.S. Department of Energy (DOE), Div. of HEP, Contract DE-AC02-06CH11357.

Once top quarks are found, because they are heavy they will allow many new tests of the standard model (SM) and new probes of physics at the 100-GeV scale. In this paper we show how to test the standard-model QCD predictions for the transverse polarization of a top quark produced at the Fermilab Tevatron, Superconducting Super Collider, CERN Large Hadron Collider, and the Next Linear Collider. We also examine the most general form of the {ital W}-{ital t}-{ital b} vertex, and show how to detect effects of non-SM operators. Ways of detecting non-SM {ital CP}-violation effects in either the production or the decay of the top quarks and top antiquarks are examined.

Light scalar fields with only gravitational strength couplings are typically present in UV complete theories of physics beyond the standard model. In the early universe it is natural for these fields to dominate the energy density, and their subsequent decay---if prior to big bang nucleosynthesis---will typically yield some dark matter particles in their decay products. In this paper we make the observation that a Nonthermal ``WIMP Miracle'' may result: that is, in the simplest solution to the cosmological moduli problem, nonthermally produced WIMPs can naturally account for the observed dark matter relic density.

Recent work has shown that compactifications of F-theory provide a potentially attractive phenomenological scenario. The low energy characteristics of F-theory GUTs consist of a deformation away from a minimal gauge mediation scenario with a high messenger scale. The soft scalar masses of the theory are all shifted by a stringy effect which survives to low energies. This effect can range from 0 GeV up to ~ 500 GeV. In this paper we study potential collider signatures of F-theory GUTs, focussing in particular on ways to distinguish this class of models from other theories with an MSSM spectrum. To accomplish this, we have adapted the general footprint method developed recently for distinguishing broad classes of string vacua to the specific case of F-theory GUTs. We show that with only 5 fb^(-1) of simulated LHC data, it is possible to distinguish many mSUGRA models and low messenger scale gauge mediation models from F-theory GUTs. Moreover, we find that at 5 fb^(-1), the stringy deformation away from minimal gauge mediation produces observable consequences which can also be detected to a level of order ~ +/- 80 GeV. In this way, it is possible to distinguish between models with a large and small stringy deformation. At 50 fb^(-1), this improves to ~ +/- 10 GeV., 85 pages, 37 figures

Satellite data is accumulating that suggests and constrains dark matter physics. We argue there is a very well motivated theoretical preexisting framework consistent with dark matter annihilation being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino with mass below 200 GeV. Using the program GALPROP we study the annihilation products and backgrounds together. Antimatter and gammas from annihilating winos contribute below this energy. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier experiments, and explain why the antiproton analysis was misunderstood by earlier papers. Wino annihilation does not describe the Fermi e+ + e- data (except partially below ~ 100 GeV). At higher energies we expect astrophysical mechanisms, and we simply parameterize them so the combination can describe all the data. We emphasize several predictions for satellite data to test the wino interpretation, particularly the turndown of the positron and antiproton spectra above 100 GeV. Most other interpretations require a large rise in the positron rates above 100 GeV. We focus on studying this well-motivated and long predicted wino interpretation, rather than comparisons with other interpretations. We emphasize that interpretations also depend very strongly on assumptions about the cosmological history of the universe, and on propagation of antiprotons and positrons in the galaxy. The winos PAMELA is observing arose from some non-thermal sources such as moduli decay rather than a universe that cooled in thermal equilibrium after the big bang. Then it is appropriate to normalize the wino density to the local relic density, and no "boost factors" are needed to obtain the reported PAMELA rates., Comment: Correct primary electron injection index

The transverse polarization of the muon (${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{\perp}}}$) in the decay ${\mathit{K}}^{+}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{0}$${\mathrm{\ensuremath{\mu}}}^{+}$${\ensuremath{\nu}}_{\mathrm{\ensuremath{\mu}}}$ is a very useful tool for studying CP violation because a detectable nonzero ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{\perp}}}$ can only arise from physics beyond the standard model. Further, ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{\perp}}}$ is interesting because it probes a different region of parameter space than many other CP-violating observables. To help justify an experimental search, we present three models which give ${\mathit{P}}_{\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{\perp}}}$\ensuremath{\gtrsim}${10}^{\mathrm{\ensuremath{-}}3}$ and which are not contradicted by other experimental data. We also comment on K\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\mu}\ensuremath{\mu} decays.

In the standard model a right-handed neutrino can appear only by mixing with the left-handed neutrinos. Precise electroweak data constrain this mixing. We consider models in which the mixing is not proportional to neutrino masses. We have analyzed data and constraints on mt,mH with and without mixing (sine) of neutrinos with new inert fermions. For universal v mixing, sine=0.09; if only vτ mixes, sineτ =0.22. Thus vτ data, Γτ and ΓinvZ, if interpreted without caution, perhaps favor a nonzero vτ mixing and the existence of heavy neutral fermions.

We continue our study of the low energy implications of $M$ theory vacua on ${G}_{2}$-manifolds, undertaken in B. S. Acharya, K. Bobkov, G. L. Kane, P. Kumar, and J. Shao, Phys. Rev. D 76, 126010 (2007); B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006), where it was shown that the moduli can be stabilized and a TeV scale generated, with the Planck scale as the only dimensionful input. A well-motivated phenomenological model, the ${G}_{2}$-MSSM, can be naturally defined within the above framework. In this paper, we study some of the important phenomenological features of the ${G}_{2}$-MSSM. In particular, the soft supersymmetry breaking parameters and the superpartner spectrum are computed. The ${G}_{2}$-MSSM generically gives rise to light gauginos and heavy scalars with wino lightest supersymmetric particles when one tunes the cosmological constant. Electroweak symmetry breaking is present but fine-tuned. The ${G}_{2}$-MSSM is also naturally consistent with precision gauge coupling unification. The phenomenological consequences for cosmology and collider physics of the ${G}_{2}$-MSSM will be reported in more detail soon.

We construct LHC signature footprints for four semirealistic string/M theory vacua with a minimal supersymmetric standard model visible sector. We find that they all give rise to limited regions in LHC signature space and are qualitatively different from each other for understandable reasons. We also propose a technique in which correlations of LHC signatures can be effectively used to distinguish among these string theory vacua. We expect the technique to be useful for more general string vacua. We argue that further systematic analysis with this approach will allow LHC data to disfavor or exclude major 'corners' of string/M theory and favor others. The technique can be used with limited integrated luminosity and improved.

We review what can (and cannot) be learned if dark matter is detected in one or more experiments, emphasizing the importance of combining LHC data with direct, astrophysical and cosmological probes of dark matter. We briefly review the conventional picture of a thermally produced WIMP relic density and its connection with theories of electroweak symmetry breaking. We then discuss both experimental and theoretical reasons why one might generically expect this picture to fail. If this is the case, we argue that a combined effort bringing together all types of data -- combined with explicitly constructed theoretical models -- will be the only way to achieve a complete understanding of the dark matter in our universe and become confident that any candidate actually provides the relic density., Comment: 25 pages, 2 figures, Invited review for Modern Physics Letters A

Recently the PAMELA satellite-based experiment reported an excess of galactic positrons that could be a signal of annihilating dark matter. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties associated with their propagation. It is not unreasonable to take this well-motivated candidate seriously, at present, in part because it can be tested in several ways soon. The forthcoming PAMELA data on higher energy positrons and the FGST (formerly GLAST) data, should provide important clues as to whether this scenario is correct. If correct, the wino interpretation implies a cosmological history in which the dark matter does not originate in thermal equilibrium., Comment: 7 pages, 4 figues

We address the cosmological moduli/gravitino problems and the issue of too little thermal but excessive non-thermal dark matter from the decays of moduli. The main examples we study are the G2-MSSM models arising from M theory compactifications, which allow for a precise calculation of moduli decay rates and widths. We find that the late decaying moduli satisfy both BBN constraints and avoid the gravitino problem. The non-thermal production of wino LSPs, which is a prediction of G2-MSSM models, gives a relic density of about the right order of magnitude., Comment: 41 pages, 5 figures, references and minor comments added

Vector-like fermions are characterized by large neutral current decay rates, in particular into Higgs bosons. If they exist, their clear signals at hadron colliders open a window to Higgs detection, especially to the intermediate Higgs mass region. We discuss in some detail rates and signatures for simple cases., Research supported in part by the US DOE by CICYT and by the Spain-U.S. committee.

If supersymmetry is discovered at the LHC, the measured spectrum of superpartner masses and couplings will allow us to probe the origins of supersymmetry breaking. However, to connect the collider-scale Lagrangian soft parameters to the more fundamental theory from which they arise, it is usually necessary to evolve them to higher scales. The apparent unification of gauge couplings restricts the possible forms of new physics above the electroweak scale, and suggests that such an extrapolation is possible. Even so, this task is complicated if the low scale spectrum is not measured completely or precisely, or if there is new physics at heavy scales beyond the reach of collider experiments. In this work we study some of these obstacles to running up, and we investigate how to get around them. Our main conclusion is that even though such obstacles can make it very difficult to accurately determine the values of all the soft parameters at the high scale, there exist a number of special combinations of the soft parameters that can avoid these difficulties. We also present a systematic application of our techniques in an explicit example., 39 pages, 14 figures

In a recent paper \cite{Acharya:2006ia} it was shown that in $M$ theory vacua without fluxes, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of \cite{Acharya:2006ia} in more detail and generalizes them, finding an essentially unique de Sitter (dS) vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV - 100 TeV range., Comment: 73 pages, 39 figures, Minor typos corrected, Figures and References added

This short article is written as a token of my respect for Richard Arnowitt and his theoretical and phenomenological physics. I focused on his favorite superpartner signature, trilepton events, and pointed out that in M theory that signature would have been absent because two of the leptons came from the decay wino → bino + Z but in M theory the decay wino → bino + Higgs dominates.

The worldview of physicists working on unification theories has been changing rapidly recently. That change culminated in March, at the 46th annual Recontres de Moriond conference in Les Arcs. France, with the announcement of some startling data from CERN's Large Hadron Collider (LHC).

An old idea for explaining the hierarchy is strong gauge dynamics. We show that such dynamics {\it also} stabilises the moduli in $M$ theory compactifications on manifolds of $G_2$-holonomy {\it without} fluxes. This gives stable vacua with softly broken susy, grand unification and a distinctive spectrum of TeV and sub-TeV sparticle masses., Comment: 4 pages, no figures. Minor typos corrected, References Added

We propose a model for early universe cosmology without the need for fundamental scalar fields. Cosmic acceleration and phenomenologically viable reheating of the universe results from a series of energy transitions, where during each transition vacuum energy is converted to thermal radiation. We show that this `cascading universe' can lead to successful generation of adiabatic density fluctuations and an observable gravity wave spectrum in some cases, where in the simplest case it reproduces a spectrum similar to slow-roll models of inflation. We also find the model provides a reasonable reheating temperature after inflation ends. This type of model may also be relevant for addressing the smallness of the vacuum energy today., 13 pages, 4 figures, published version

18 páginas, 6 figuras, 12 tablas.-- et al., High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e + e - linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.

We argue that it is possible to address the deeper LHC Inverse Problem, to gain insight into the underlying theory from LHC signatures of new physics. We propose a technique which may allow us to distinguish among, and favor or disfavor, various classes of underlying theoretical constructions using (assumed) new physics signals at the LHC. We think that this can be done with limited data $(5-10 fb^{-1})$, and improved with more data. This is because of two reasons -- a) it is possible in many cases to reliably go from (semi)realistic microscopic string construction to the space of experimental observables, say, LHC signatures. b) The patterns of signatures at the LHC are sensitive to the structure of the underlying theoretical constructions. We illustrate our approach by analyzing two promising classes of string compactifications along with six other string-motivated constructions. Even though these constructions are not complete, they illustrate the point we want to emphasize. We think that using this technique effectively over time can eventually help us to meaningfully connect experimental data to microscopic theory., Comment: 50 Pages, 13 Figures, 3 Tables, v2: minor changes, references added

Suppose we could understand the laws of nature that govern the particles and their interactions, and in addition why the laws are as they are, and also how the universe evolved and perhaps even how it originated—an active research area today That understanding—a theory—would be formulated not in terms of everyday units, but rather units built from constants such as the speed of light, Planck's constant and Newton's constant. From these constants one obtains the natural scales: the Planck length (∼10−33 cm) and the Planck mass (MP∼1019 GeV/c2). I will call this theory the primary theory, a name I like because it suggests that as we go through a hierarchy of effective theories, from macroscopic sizes to atoms to nuclei, we end at a primary one that is not related to another at a deeper level.

String theories in principle address the origin and values of the quark and lepton masses. Perhaps the small values of neutrino masses could be explained generically in string theory even if it is more difficult to calculate individual values, or perhaps some string constructions could be favored by generating small neutrino masses. We examine this issue in the context of the well-known three-family standard-like Z_3 heterotic orbifolds, where the theory is well enough known to construct the corresponding operators allowed by string selection rules, and analyze the D- and F-flatness conditions. Surprisingly, we find that a simple see-saw mechanism does not arise. It is not clear whether this is a property of this construction, or of orbifolds more generally, or of string theory itself. Extended see-saw mechanisms may be allowed; more analysis will be needed to settle that issue. We briefly speculate on their form if allowed and on the possibility of alternatives, such as small Dirac masses and triplet see-saws. The smallness of neutrino masses may be a powerful probe of string constructions in general. We also find further evidence that there are only 20 inequivalent models in this class, which affects the counting of string vacua., Comment: 18 pages in RevTeX format. Single-column postscript version available at http://sage.hep.upenn.edu/~bnelson/singpre.ps

The rare decay $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{K}_{S}$ is a well-known probe of physics beyond the standard model because it arises only through loop effects yet has the same time-dependent CP asymmetry as $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\psi}{K}_{S}.$ Motivated by recent data suggesting new physics in $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{K}_{S},$ we look to supersymmetry for possible explanations, including contributions mediated by gluino loops and by Higgs bosons. Chirality-preserving LL and RR gluino contributions are generically small, unless gluinos and squarks masses are close to the current lower bounds. Higgs contributions are also too small to explain a large asymmetry if we impose the current upper limit on ${B(B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}).$ On the other hand, chirality-flipping LR and RL gluino contributions can provide sizable effects and while remaining consistent with related results in $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\psi}{K}_{S},$ $\ensuremath{\Delta}{M}_{s},$ $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{s}\ensuremath{\gamma}$ and other processes. We discuss how the LR and RL insertions can be distinguished using other observables, and we provide a string-based model and other estimates to show that the needed sizes of mass insertions are reasonable.

We propose an approach to explaining why naive large quantum fluctuations are not the right estimate for the cosmological constant. We argue that the universe is in a superposition of many vacua, in such a way that the resulting fluctuations are suppressed by level repulsion to a very small value. The approach combines several aspects of string theory and the early history of the universe, and is only valid if several assumptions hold true. The approach may also explain why the effective cosmological constant reamins small as the universe evolves though several phase transitions. It provides a non-anthropic mechansim leading to a small, non-zero cosmological constant., Talk given at Rencontres de Moriond, 2004 by G.L. Kane

We study the implications for the minimal supersymmetric standard model (MSSM) of the absence of a direct discovery of a Higgs boson at LEP. First we exhibit 15 physically different ways in which one or more Higgs bosons lighter than the LEP limit could still exist. For each of these cases -- as well as the case that the lightest Higgs eigenstate is at, or slightly above, the current LEP limit -- we provide explicit sample configurations of the Higgs sector as well as the soft supersymmetry breaking Lagrangian parameters necessary to generate these outcomes. We argue that all of the cases seem fine-tuned, with the least fine-tuned outcome being that with Higgs mass near 115 GeV. Seeking to minimize this tuning we investigate ways in which the ``maximal-mixing'' scenario with large top-quark trilinear A-term can be obtained from simple string-inspired supergravity models. We find these obvious approaches lead to heavy gauginos and/or problematic low-energy phenomenology with minimal improvement in fine-tuning., 24 pages; uses RevTeX

We present some phenomenology of a new class of intersecting D-brane models. Soft SUSY breaking terms for these models are calculated in the u - moduli dominant SUSY breaking approach (in type IIA). In this case, the dependence of the soft terms on the Yukawas and Wilson lines drops out. These soft terms have a different pattern compared to the usual heterotic string models. Phenomenological implications for dark matter are discussed., Comment: 29 pages, 1 figure, References added

Predictions for the properties and detectability of cold dark matter (CDM) made of the lightest supersymmetric partner (LSP) are presented. This work differs from previous ones by first including all theoretical and experimental constraints in constructing the supersymmetric models, so that all parameters used are known to be consistent with other requirements, second by not assuming values for parameters but surveying the entire parameter space, and third by considering all methods of CDM detection in a consistent way. This talk is based on work with E. Diehl, C. Kolda, L. Roszkowski, and J. Wells.